RAM usage remain high even the vps are all's stopped

[openaspace]

Helloooo

I have proxmox installation with zfs on 32gb ram i7 and raid 10 conf.

With vps on I have 60% ram usage, but when I power off all machines , the ram usage go down only to 50%...
And only if I reboot.. It return to normal usage.

Any advice?

 

[Pontius]

That's ZFS eating up you RAM.
Have a look at `/proc/spl/kstat/zfs/arcstats` next time your RAM usage gets up.

 

[openaspace]

That's ZFS eating up you RAM.
Have a look at `/proc/spl/kstat/zfs/arcstats` next time your RAM usage gets up.

I was suspecting..

 

[openaspace]

Here the answer from Reddit

https://www.reddit.com/r/homelab/co...kidhl?utm_medium=android_app&utm_source=share

 

[LnxBil]

It return to normal usage.

Sorry, but a full RAM is normal, empty is the worst thing you can have. We discussed this a gazilion times already, please also read this.

 

[openaspace]

Sorry, but a full RAM is normal, empty is the worst thing you can have. We discussed this a gazilion times already, please also read this.

Than you.
Is that using an hypervisor.. you are led to think that by turning off a virtual machine, the RAM becomes free ...

 

[LnxBil]

Than you.
Is that using an hypervisor.. you are led to think that by turning off a virtual machine, the RAM becomes free ...

Why should it be free? Have you read the page? Normally, your VMs use the host page cache and in case of ZFS its ARC, so even after tuning off your VM, the data already read is still in the RAM so that if you start your VM, everything will be blazing fast, because the data is already in the RAM and does not have to be read from roughly 1000000x times slower harddisk. Linux just shows the RAM as used, whereas Windows would show it as free.

 

[openaspace]

Why should it be free? Have you read the page? Normally, your VMs use the host page cache and in case of ZFS its ARC, so even after tuning off your VM, the data already read is still in the RAM so that if you start your VM, everything will be blazing fast, because the data is already in the RAM and does not have to be read from roughly 1000000x times slower harddisk. Linux just shows the RAM as used, whereas Windows would show it as free.

Yes yes all clear
Is only that don't return a clear setup of the ram really available when I need to set new virtual machine or resize existing one

 

[LnxBil]

Yes yes all clear
Is only that don't return a clear setup of the ram really available when I need to set new virtual machine or resize existing one

ZFS has its dedicated ARC that is per default half the RAM so you can set your VMs at most half of the RAM for best performance. If you want to change the ratio (and get slower performance), you can adapt the maximum RAM used for ZFS and have more RAM available for machines. At the moment, you cannot reclaim the RAM used by ZFS when starting a VM (a real one, not a container).

 

[openaspace]

ZFS has its dedicated ARC that is per default half the RAM so you can set your VMs at most half of the RAM for best performance. If you want to change the ratio (and get slower performance), you can adapt the maximum RAM used for ZFS and have more RAM available for machines. At the moment, you cannot reclaim the RAM used by ZFS when starting a VM (a real one, not a container).

oooK thank you.
sorry for my ignorance, but this mean that i will avoid to use more than the available host memory for VPS?
if yes... this reduce a lot the usable vps ram.. if the 50% is used by zfs..

 

[LnxBil]

sorry for my ignorance, but this mean that i will avoid to use more than the available host memory for VPS?
if yes... this reduce a lot the usable vps ram.. if the 50% is used by zfs..

Yes, that is the cross to bear. You can limit the amount with this, but your system will be slower then.